Which of the following amino acid has its PKa value within physiological range?

Histidine has a PKa value of its R group in the physiologic pH range. PKa represents the relative proton donating capacity of amino acids and each amino acid has its own unique PKa value. Other imidazole containing dipeptides with pKa between 6.8 and 7 found in mammalian skeletal muscle are carnosine(beta alanyl L histidine) and anserine(beta alanyl L1 methylhistidine). Ref: Principles of Exercise Biochemistry edited by J. R. Poomans 4th edn page 252. Introduction to Natural Products Chemistry edited by Rensheng Xu, page 149